Evaluation of early and late postoperative flow capacity of internal thoracic artery bypass by means of stress Doppler echocardiography

Abstract

Arterial revascularization with the internal thoracic artery (ITA) has shown exceptional long-term results, even though early hypoperfusion can occur and can cause ischemia and contractile dysfunction. Therefore, it is still controversial as to whether the bypass vessel can guarantee the required demand for blood flow during the early postoperative (EPO) phase or whether this is only possible a long time after the operation. This question is important particular in the early postoperative phase to manage afterload and reduce left ventricular oxygen demand. Therefore, stress Doppler echocardiography was performed to assess EPO and late postoperative (LPO) flow capacity after minimal-invasive coronary artery bypass grafting (MIDCAB) in subjects with single vessel disease. Doppler echocardiography was performed after MIDCAB in 15 patients (mean age 65 years+/-12 standard deviation) in the EPO (15 days) and LPO (266 days) at rest and under stress. The mean diastolic velocity (MDV) as a measure for the coronary perfusion in the bypass-graft was comparable (30.9+/-14.5 EPO to 30.8+/-13.9 cm/s LPO, P>0.05) for both settings (early vs. late). In both tests, the stress reactions by means of handgrip maneuver lead to comparable increases in blood flow: MDV 65.0+/-54.4% (EPO) to 62.5+/-53.7% n.s. (LPO). The flow increase in the bypass graft was just as similar [48.2+/-46.2% (EPO) to 51.1+/-41.6% n.s. (LPO)]. The stress echocardiography revealed for the first time that the ITA-graft after MIDCAB-operation is able to produce the same flow reserve through the EPO phase as well as the LPO phase. Restrictions to a maximum early flow adaptation are not justified. Thus, particularly a patient with severe comorbidities or higher age should be mobilized in the EPO phase to minimize the postoperative complications without risk of myocardial ischemia caused by impaired early blood flow through recent implanted ITA. This method for assessment of ITA blood flow allows for long-time observations and can detect disturbances in perfusion at an early stage.